(1) Field of the Invention
The present invention relates to a shoe sole having improved lateral and medial stability. In particular, the present invention pertains to a shoe sole having a stabilizing apparatus either inserted into the sole or formed in the sole, where the stabilizing apparatus alters the ability of the shoe sole to resist compression at opposite left and right sides of the sole where the apparatus is inserted, thereby improving the lateral and medial stability of the shoe. The stabilizing apparatus of the present invention is particularly useful in shoe soles employing fluid filled bladders or pads as cushions.
(2) Description of the Related Art
Many types of shoe soles are required to have a certain amount of cushioning to absorb shocks from footstep impact and thereby protect the foot from these shocks. This is particularly true in athletic footwear where the foot is exposed to repeated shocks from footstep impact in running and other athletic activities.
Prior art shoes have been developed employing a variety of different cushioning devices between the foot and the outsole of the shoe to protect the foot from the shock of footstep impact. These prior art cushioning devices range from merely constructing the shoe sole from a softer, more resilient material to incorporating fluid filled pads or bladders in the sole of a shoe.
In many shoe soles designed to increase the cushioning effects of the shoe sole, the increased resiliency or "softness" of the shoe sole provides no resistance to the tendency of a shoe wearer's foot to rotate relative to the leg upon impact. The tendency for excessive lowering of the medial margin of the foot, or excessive pronation, and the tendency for excessive raising of the medial margin of the foot, or supination, have the potential of causing injuries to the wearer of the shoe.
Concepts have been developed to increase the lateral and medial stability of the shoe. One such concept is disclosed in U.S. Pat. No. 4,402,146, assigned to the assignee of the present invention. The aforesaid patent discloses a shoe having increased lateral stability comprising a pair of tabs extending from opposite sides of the outsole of the shoe to the heel counter of the shoe, thereby resiliently connecting the outsole to the heel counter and increasing the lateral medial stability of the shoe. The tabs are formed as an integral part of the shoe outsole and are bonded to a heel wedge layer and midsole layer of the shoe sole as well as the heel counter.
The shoe sole stabilizer described above is disadvantaged in that it is adhered over the outside of the shoe sole and heel counter and is visible. This requires that the tabs be designed in such a way to make them a part of the overall design appearance of the shoe. Furthermore, the tabs being adhered to the extreme outer sides of the heel wedge and midsole reduce the ability of the tabs to resist compression of the heel wedge and midsole in the areas of the wedge and midsole inside the shoe surrounding the wearer's foot.
The present invention overcomes disadvantages associated with prior art shoe sole lateral and medial stabilizers by providing a lateral and medial stabilizer for a shoe sole that is contained inside a sole layer or member of the shoe sole. The stabilizer of the invention serves to increase or decrease the resistance to compression of the shoe sole member at positions adjacent to the opposite left and right sidewalls of the sole member, without significantly effecting the cushioning ability of a middle portion of the sole member between its left and right sidewalls. In variant embodiments of the invention the stabilizer is employed to increase or decrease the resistance to compression of the opposite left and right sidewalls of the shoe sole member. Furthermore, the stabilizing apparatus of the present invention is ideally suited for use in shoe soles incorporating fluid filled pads or bladders, thereby combining the desirable cushioning ability of the fluid filled pad with the improved lateral and medial stability provided by the apparatus of the present invention.